Congress and the White House appear to be headed for a constitutional showdown. The House of Representatives is poised to hold Joshua Bolten, the White House chief of staff, and Harriet Miers, a former White House counsel, in contempt for failing to comply with subpoenas in the United States attorneys scandal. If the Justice Department refuses to enforce the subpoenas, as seems likely, Congress will have to decide whether to do so. Washington lawyers are dusting off an old but apparently sturdy doctrine called “inherent contempt” that gives Congress the power to bring the recalcitrant witnesses in — by force, if necessary.

What we know that Congress has learned in its investigation of the purge of nine top federal prosecutors is disturbing. Cases appear to have been brought against Democrats and blocked against Republicans to help Republicans win elections. The stakes have grown steadily: it now seems that innocent people, like Georgia Thompson, a Wisconsin civil servant, may have been jailed for political reasons. Congress has a duty to find out what happened.